Fxs and Structures of Dermis- strong, flexible, conn tissue- cells include fibroblasts (cells that synthesize the extracellular matrix and collagen), macrophages, and occasionally mast cells and white blood cells- 2 layers, fx, and strutureso papillary-composed of areolar conn tissue with collagen and elastic fibers and blood vessels. Contains capillary loops (nutrients for the epidermal layer, Meissner’s corpuscles (sense light touch and vibrations, many found on fingertips) and nerve endingso reticular- ~80% of the thickness of dermis. Collagen fibers provide strength/resiliency. Stretch marks due to tears in the collagen of dermis- contains several partso structural protein fiberso sweat glandso hair follicleso sebaceous glandso nail rootso nerve endings- scars/tattoosGLANDS- two main types of sweat glands:o eccrine (merocrine) sweat glands: 304 million, abundant on palms, soles, foreheado apocrine sweat glands are confined to axillary and anogenital areas- sebaceous (oil) glandso widely distributed, most develop from hair follicles, become active at pubertyo sebum secreted oily holocrine secretion bactericidal softens hair and skino acne plugged sebaceous ducts whitehead blackheado treatments benzoyl peroxide-antibacterial salicyclic acid-unclogs pores antibiotics kill bacteria (Dioxycycline, tetracycline, erythromycin)HAIR- fxs: o alerting body to presence of foreign particle (such as insect or irritant) on the skino guarding the scalp agst physical trauma, heat loss, sunlighto visual identification: hair characteristics help determine sex, age, identificationo insulation: anorexia- location: entire surface except palms, soles, lips, nipples, and portions of external genitalia- consists of dead keratinized cells- containds hard keratin; more durable than soft keratin of skin- associated with glands and a muscle- hair pigments: melanins in _____o gray/white hair: decreased melanin production- hair rooto lower part of the hair o attached to the integument- hair shafto upper part of the hairo not attached to the integument- one hair is called a pilus- types of hairo vellus is the hair at birth (peach fuzz)o terminal hair is present in specific regions normal adult hairo lanugo hair is fine baby hair, last trimester of pregnancy and sometimes on babies but falls off- _____pale fine body hair of children and adult females- terminal is coarse, long hair of eyebrows, scalp, axillary, and pubic HAIR GROWTH- growth phase (weeks to yrs) followed by regressive stage and resting phase (1-3 mos.)- growth phase varies (6-10 yrs in scalp, 3-4 mos. In eyebrows)- hair grows at rate of ~.3 mm/day and lose 10-100 hairs a day- phases of growth:o active phase of the hair growth cycle anageno catagen transitional phase of the hair cycle bw growth and resting of the hair follicleo telogen- the resting phase of the hair growth cycle- hair follicleo extends from the epidermal surface into the dermiso hair begins deep in the dermis: the hair papilla contains capillaries and nerves that provide nourishment the hair bulb produces hair matrix hair matrix epithelium is one of the fastest growing cell populations in human bodyo a hair follicle is a part of the skin that grows hairo internal root sheath: the inner layer contacts the cuticle in lower hair rooto external root sheath extends from skin surface to hair matrixo glassy membrane (basement membrane): a dense conn tissue sheath contacts conn tissues of dermis- hair anatomyo central medullao cortex surrounds medullao cuticle on outside of cortex is most heavily keratinized- hair pigments: melanin typeso pheomelanin is responsible for the yellowish-blond to red colorso eumelanin is responsible for the brown to black shades- hair follicle receptor (root hair plexus)o sensory nerve endings around each hair bulb stimulated by bending a hair, responds to initial movement- arrector pili muscleso smooth muscle attached to follicleo responsible for goose bumps- HAIR THINNING AND BALDNESSo ____is hair thinning in both sexeso true baldness genetically determined and sex-influenced condition male-pattern baldness is caused by follicular response to
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